Color and Distribution of Pigment Cells in the Skin of the Zebrafish

Abstract

In order to understand how pigment cells participate in the color pattern formation, we examined the distribution of pigment cells in the skin of the zebrafish having alternate stripes of deep blue and white. In the skin of deep blue stripe areas, iridophores assuming blue coloration are distributed over the melanophore layer, while in the brownish dorsal skin, melanophores and xanthophores overlie iridophores. Within such iridophores, very thin light-reflecting platelets are stacked regularly at an equal distance from one another, and the platelets are inclined at a constant angle. Probably, the iridophores manifest blue color through multilayered thin-film interference of non-ideal type. In the skin of deep blue stripe regions, another type of iridophores, in which the reflecting platelets lie parallel to the dermis, was also observed below melanophores. It is likely that thin-film interference of ideal-type is responsible for the silvery tones generated by the iridophores. In the skin of white stripe regions, iridophores exist densely in 3 or 4 layers, and xanthophores overlie the iridophore layers. Thus, it has been shown that the difference in pigment cell organization in each region is involved in the color pattern formation in the zebrafish.